The increasing reliance on communication networks to transmit more complex data, such as voice and video traffic, is causing a very high demand for bandwidth. To resolve this demand for bandwidth, communications networks are relying upon optical fiber to transmit this complex data. Conventional communication architectures that employ coaxial cables are slowly being replaced with communication networks that comprise only fiber optic cables. One advantage that optical fibers have over coaxial cables is that a much greater amount of information can be carried on an optical fiber.
While the FTTH optical network architecture has been a dream of many data service providers because of the aforementioned capacity of optical fibers, implementing the FTTH optical network architecture may encounter some problems associated with legacy systems that are in current use by subscribers. For example, many subscribers of data service providers use set top terminals (STTs) to receive and transmit information related to video services. The conventional set top terminals are usually coupled to a coaxial cable. The coaxial cable, in turn, is then connected to fiber optic cables in a hybrid fiber-coax (HFC) system. The coaxial cable from the set top terminals in combination with the fiber optic cables provide a two way communication path between the set top terminal and the data service hub for purposes such as authorizing a subscriber to view certain programs and channels.
For example, conventional set top terminals coupled to coaxial cables may provide impulse pay-per-view services. Impulse pay-per-view services typically require two way communications between the set top terminal and the data service provider. Another exemplary service that may require two-way communication passed between the set top terminal and the data service provider is video-on-demand (VOD) services.
For video-on-demand services, a subscriber can request a program of his choosing to be played at a selected time from a central video file server at the data service hub. The subscriber's VOD program request is transmitted upstream on a return channel that comprises coaxial cables coupled to fiber optic cables. With the VOD service, a subscriber typically expects VCR-like control for these programs which includes the ability to “stop” and “play” the selected program as well as “rewind” and “fast forward” the program.
In conventional HFC systems, a return RF path from the subscriber to the data service hub is provided. The RF return path is needed because a conventional set top terminal usually modulates its video service upstream data onto an analog RF carrier. While the video service upstream data may be modulated onto an RF carrier, it is recognized that the upstream data may be in digital form.
A RF return path typically comprises two-way RF distribution amplifiers with coaxial cables and two-way fiber optic nodes being used to interface with fiber optic cables. A pair of fiber optic strands can be used to carry the radio frequency signals between the head end and node in an analog optical format. Each optical cable of the pair of fiber optic strands carries analog RF signals: one carries analog RF signals in the downstream direction (toward the subscriber) while the other fiber optic cable carries analog RF signals in the reverse or upstream direction (from the subscriber). In a more recent embodiment, the upstream spectrum (typically 5–42 MHz in North America) is digitized at the node. The digital signals are transmitted to the headend, where they are converted back to the analog RF spectrum of 5–42 MHz. This process typically uses high data rates (at least 1.25 Gb/s) and a fiber or wavelength dedicated to return traffic from one or two nodes.
Unlike HFC systems, conventional FTTH systems typically do not comprise a return RF path from the subscriber to the data service hub because most of the return paths comprise only fiber optic cables that propagate digital data signals as opposed to analog RF signals. In conventional FTTH systems, a downstream RF path is usually provided because it is needed for the delivery of television programs that use conventional broadcast signals. This downstream RF path can support RF modulated analog and digital signals as well as RF modulated video return control signals for any set top terminals that may be used by the subscriber. However, as noted above, conventional FTTH systems do not provide for any capability of supporting a video control return path for video control return signals generated by the legacy set top terminal.
Some conventional legacy set top terminals are being equipped with dedicated data cables in addition to coaxial cables in order to support upstream digital communications. For example, some conventional legacy set top terminals can include Ethernet data ports in order to support Category 5 type cabling. These dedicated cables for upstream digital communications are usually connected to an interface located on a side of structure such as a home or office building. The interface typically has hardware used to convert the upstream digital communications to the optical domain.
While the legacy set top terminals having the combination of coaxial cables for downstream analog communications and dedicated data cables for upstream digital communications may have solved the return path problem of the conventional terminals discussed above, it has created other problems: entire structures such as homes and office buildings will need rewiring such that the dedicated data cables are positioned within the structures and adjacent to the existing coaxial cables. Such rewiring can be very difficult and costly because finished interiors of the structures will be disturbed or damaged in order to make room for the new dedicated data cables.
Accordingly, there is a need in the art for the system and method for communicating optical signals between a data service provider and a subscriber that can eliminate the need for damaging a structure to house new cables. There is also a need in the art for a system and method that provides a video control return path for legacy video service terminals that can minimize the hardware needed to support upstream video control return signals. A further need exists in the art for a system and method that provides a video control return path that can minimize cabling but than can support upstream digital contention network protocols such as Ethernet formatted packets. Another need exists in the art for supporting legacy video service controllers and terminals with an all optical network architecture external to the subscriber's location.